Expression of viral genes in both uninfected and Rous sarcoma virus infected cells will be analyzed in detail to determine the level at which these genes are regulated, the molecular basis for this regulation, and the relationship between endogenous viral genes and virus-induced neoplasia. Highly specific complementary DNA probes, representing individual viral genes, or specific regions of the genome, are being isolated and utilized for molecular hybridization analyses of gene expression. The study will include analyses of RNA synthesis, processing, transport, and utilization, and will utilize probes specific for the sarcoma and envelope glycoprotein genes. Efforts will also be made to isolate DNA corresponding to a postulated gene which induces leukemia in virus-infected animals. Specific mRNAs will be used in the wheat germ system in an effort to synthesize the transforming protein(s) in vitro. BIBLIOGRAPHIC REFERENCES: Hanafusa, T., Hanafusa, H., Metroka, C.E., Hayward, W.S., Rettenmier, C.W., Sawyer, R.C., Dougherty, R.M., and diStefano, H.S. (1976). Pheasant virus: new class of ribodeoxyvirus. Proc. Natl. Acad. Sci. U.S.A. 73, 1333-1337. Hayward, W.S., Wang, S.Y., Urm, E., and Hanafusa, H. (1976). Transcription of the avian RNA tumor virus glycoprotein gene in uninfected and infected cells. In Animal Virology; ICN-UCLA Symposia on Molecular and Cellular Biology. (in press).